Gas turbines are used in many fields for driving generators or driven machines. In this case, the energy content of a fuel is used for producing a rotational movement of a turbine shaft. To this end, the fuel is combusted in a combustion chamber, wherein compressed air is supplied from an air compressor. The operating medium, which is produced in the combustion chamber as a result of combustion of the fuel, is directed in this case under high pressure and under high temperature via a turbine unit, which is connected downstream to the combustion chamber, where it is expanded, performing work.
For producing the rotational movement of the turbine shaft, in this case a number of rotor blades, which are customarily assembled into blade groups or blade rows, are arranged on this and drive the turbine shaft via an impulse transfer from the operating medium. For flow guiding of the operating medium, moreover, stator blades, which are connected to the turbine casing and assembled to form stator blade rows, are customarily arranged between adjacent rotor blade rows. These stator blades are fastened via a blade root on a customarily hollow cylindrical or hollow conical stator blade carrier and on their side facing the turbine axis are fastened via a blade tip on an inner ring which is common to the respective stator blade row. In the case of stationary gas turbines, this inner ring frequently consists of an upper and a lower half which are interconnected via flanges.
In the design of such gas turbines, in addition to the achievable power, a particularly high efficiency is customarily a design aim. An increase of the efficiency can basically be achieved in this case, for thermodynamic reasons, by an increase of the discharge temperature at which the operating medium flows out of the combustion chamber and flows into the turbine unit. In this case, temperatures of about 1200° C. to 1500° C. are aimed at, and also achieved, for such gas turbines.
Such high temperatures of the operating medium, however, lie far above the melting temperature of the component materials which are used in the discharge region of the combustion chamber, for example, so that the critical components have to be intensely cooled and protected with complex coating systems for ensuring the necessary function of the gas turbine. In this case, it cannot be excluded occasionally that despite application of these highly developed and frequently tested technologies for cooling and coating the blades a premature exchange of stator blades becomes necessary since the blade function, as result of partial loss of the coating or closing off of cooling air holes, for example, is impermissibly impaired. In the case of large stationary gas turbines, such an exchange measure can last at best several days, but on average about two weeks, so that as a result an undesired and expensive interruption of the operation of the gas turbine or of a gas and steam turbine power plant, in which the gas turbine is used, is brought about.
A stator blade ring for a turbomachine is known from U.S. Pat. No. 3,300,180. The stator blade ring comprises a stator blade carrier which consists of two clamping rings which in each case are assembled from two 180° large segments. Stator blade segments are clamped between the two clamping rings, forming a stator blade ring. In this case, the stator blade segments are further stabilized on their inner end by means of an inner ring.
It is disadvantageous, however, that for removal of a stator blade segment which is to be exchanged the one or both segment(s) of one of the two clamping rings has or have to be completely removed. This is associated with increased time consumption and greater space requirement.
Furthermore, a turbine stator blade carrier, which extends over the entire axial length of the turbine unit, is known from US 2005/0132707 A1. This is then of a multiply segmented construction in the circumferential direction.